1. Field of the Invention
The present invention relates to an optical disk recording method and optical disk recording apparatus in which contents information is recorded in optical disks such as a compact disk-recordable (CD-R) and CD-rewritable (CD-RW).
2. Discussion of the Related Art
In a recordable optical disk conforming to CD standard such as CD-R, a guide groove called a pregroove is formed beforehand along a track in a disk manufacturing process. The pregroove wobbles (meanders), and a wobbling frequency thereof is detected and subjected to frequency modulation (FM) with absolute time information called Absolute Time in Pregroove (ATIP).
During the recording of contents information into the optical disk in which the pregroove is formed, a wobbling signal is extracted from a photo signal of a light reflected back from the optical disk, the wobbling signal is FM-demodulated to decode ATIP information, and an absolute position along the track on the disk is detected by the decoded ATIP information. Moreover, the detected absolute position information is used to record the contents information in the optical disk.
Additionally, types of optical disks having different recording capacities have been distributed. For example, with regard to CD-R, a disk having a recording capacity of 650 MB (megabyte) and another disk having a recording capacity of 540 MB have been marketed. The CD-R having the nominal recording capacity of 650 MB and the CD-R having the nominal recording capacity of 540 MB have the same physical length of the recordable track, but these two types of disks are different from each other in the operating speed regulated according to the progression of the absolute time information of the ATIP information extracted from the disks. That is, the track length for use in recording the absolute time information of the ATIP information differs between these two types of disks. For example, the track length for use in storing the absolute time information of ten minutes in the optical disk of 540 MB is larger than that of the optical disk of 650 MB. Therefore, the disks are different from each other in the recording density of the absolute time information. As a result, the recording capacity differs between these two types of optical disks. That is, during recording at a standard operation speed, the CD-R of 650 MB adopts a linear velocity of 1.2 m/s, the CD-R of 540 MB adopts a linear velocity of 1.4 m/s, and these linear velocities are referred to as rated linear velocities of the respective disks in the standard of the optical disk. Additionally, the “linear velocity” in the standard actually has the same meaning as the recording density. For example, the CD-R of 650 MB is different from the CD-R of 540 MB in the capacity to be recorded per unit track length. Namely, the CD-R of 650 MB is different from the CD-R of 540 MB in the recording density. The density of the CD-R of 650 MB is larger than that of the CD-R of 540 MB. The recording density obtained when the linear velocity is set to 1.2 m/s or 1.4 m/s during recording at the standard operation speed bears a reciprocal relationship to the linear velocity of 1.2 m/s or 1.4 m/s in the above-described standard. Therefore, the term “linear velocity” will be used hereinafter for representing the recording density. The value 1.4 m/s denotes an information recording pitch at the standard operation speed and is therefore used for indicating the recording density in recording the information at the linear velocity of 1.4 m/s. Similarly, the value 1.2 m/s denotes an information recording pitch at the standard operation speed and is used for indicating the recording density in recording the information at the linear velocity of 1.2 m/s. Theoretically, the greater the value of the linear velocity, the smaller the recording density, because the linear velocity is inversely proportional to the recording density.
CD-R disks having various recording capacities have been manufactured and marketed, with the user having to spend some effort in selecting a CD-R which has the recording capacity to accept the data amount to be recorded. For example, a CD-R of 650 MB may be selected in order to record music data for 74 minutes (CD-DA form: CD digital audio). A CD-R of 700 MB may be selected to record music data for 80 minutes, and a CD-R of 540 MB may be selected to record music data for 63 minutes or less. The disk-selection process is troublesome, and further, the user needs to prepare various types of CD-R disks beforehand. Moreover, when a CD-R having an appropriate recording capacity is not available, time and effort must be spent in locating and purchasing a CD-R that has the appropriate capacity. Furthermore, in general, as the recording linear density becomes smaller, it is possible to record the recording information with an improved quality level. However, in conventional operation, when data of 550 MB is recorded in a CD-R of 650 MB, a recording area of 100 MB is left unused, and a technique of effectively using such an unused extra area has not been proposed.